In recent years, a major technical challenge presented to the petroleum refining industry has been the requirement to establish alternate processes for manufacturing high octane gasoline in view of the regulated requirement to eliminate lead additives as octane enhancers as well as the development of more efficient, higher compression ratio gasoline engines requiring higher octane fuel. To meet these requirements the industry has developed non-lead octane boosters and has reformulated high octane gasoline to incorporate an increased fraction of aromatics. While these and other approaches will fully meet the technical requirements of regulations requiring elimination of gasoline lead additives and allow the industry to meet the burgeoning market demand for high octane gasoline, the economic impact on the cost of gasoline is significant. Accordingly, workers in the field have intensified their effort to discover new processes to manufacture the gasoline products required by the market place. One important focus of that research is new processes to produce high octane gasolines blended with lower aliphatic alkyl ethers as octane boosters and supplementary fuels. C.sub.5 -C.sub.7 methyl alkyl ethers, especially methyl tertiary butyl ether (MTBE) and tertiary amyl methyl ether (TAME) have been found particularly useful for enhancing gasoline octane. Therefore, improvements to the processes related to the production of these ethers are matters of high importance and substantial challenge to research workers in the petroleum refining arts.
It is known that isobutylene may be reacted with methanol over an acidic catalyst to provide methyl tertiary butyl ether (MTBE) and isoamylenes may be reacted with methanol over an acidic catalyst to produce tertiary-amyl methyl ether (TAME). In these etherification processes a problem of major importance is the separation of methanol from the etherification reaction product due to the proclivity of methanol to form a very dilute azeotropic mixture with hydrocarbons and the strong solubility of methanol in both water and hydrocarbons. Due largely to these factors, the cost associated with methanol separation and recycling in the etherification reaction represents approximately 30% of the cost of the total etherification process.
In recent years, a major development within the petroleum industry has been the discovery of the special catalytic capabilities of a family of zeolite catalyst based upon medium pore size shape selective metallosilicates. Discoveries have been made leading to a series of analogous processes drawn from the catalytic capability of zeolites. Depending upon various conditions of space velocity, temperature and pressure lower oxygenates, such as methanol can be converted in the presence of zeolite type catalyst to olefins which can oligomerize to provide gasoline or distillate or be converted further to produce aromatics. Recognizing the commonality of the feedstock and product between etherification reactions to produce high octane gasoline and zeolite catalyzed conversion reactions, interest has focused on the applicability of combined processes as an approach to advance the art in the production of high octane gasoline.
It has been discovered that under certain conditions substantial improvements in the art of high octane gasoline production can be realized in a combination or integration of etherification and aromatization processes based upon zeolite type catalyst. Accordingly, it is an object of this invention to provide a novel process for the production of high octane gasoline.
Another object of this invention is to provide a novel and cost effective process for the production of methyl tertiary alkyl ethers as octane enhancing components of high octane gasoline.
Yet a further object of the present invention is a novel process for the production of high octane gasoline through zeolite catalyzed aromatization integratd with etherification.
Yet another object of the present invention is to provide a novel process for the production of high octane gasoline rich in aromatics utilizing unreacted methanol from etherification.